Hi,
when updating a group managed SSID setting, for eg, like turning on block lan access for a SSID.
My clients get kicked off for about a minute, then intermittent performance for another minute and then back to normal.

Is this expected? If so the gui needs to warn you before hitting SAVE.

From my experience, any time you change any configuration on the AP, it reloads the config and does a soft restart. You will see spotty connectivity until everything finishes. This seems to be of a longer duration if you are using the auto channel assignments. Those channel changes cause clients to reauthenticate.